1. Field of the Invention
The present invention relates to a lenticular lens, and an image generation processing for a lenticular lens.
2. Description of the Related Art
In recent years, the development of devices dealing with images such as a digital camera, a display, and a printer, has driven demand for the reproduction of the texture of the subject, three-dimensional view, and the like.
For example, regarding the reproduction of the texture, Japanese Patent Application Laid-Open No. 10-285459 discusses a technique in which an input video signal representing an image is corrected based on a reflection light model to reproduce metallic luster. In this technique, the metallic luster is reproduced based on a luminance signal in the input video signal.
Apart from this, there is known a phenomenon in which, when images of low correlation are presented before the right and left eyes of an observer, no fusion occurs, and one of the images being predominant over the other is alternately observed. This phenomenon is called binocular rivalry since the images observed fluctuate in an unstable manner with the passage of time, and the right and left eyes seem to view with each other to observe the images. Further, as is known in the art, when images of differing in luminance are presented before the right and left eyes, there is generated a luster texture called binocular luster.
Regarding the three-dimensional view, Japanese Patent Application Laid-Open No. 10-319214 discusses a method according to which a lenticular lens is used to present parallax images before the right and left eyes of the observer to realize a three-dimensional view. According to the method, three-dimensional reproduction is realized through a combination of images obtained by dividing a plurality of parallax images into rectangular portions and synthesizing them and a lenticular lens according to the characteristics of the lenticular lens.
In general, the luster of an object, for example a state of shining by reflected light for an object, greatly depends on bidirectional reflectance distribution function (BRDF), a four-dimensional function that defines how light is reflected at an opaque surface. BRDF represents reflectance with respect to the incident angle and the output angle of the surface of an object. The lower the luster of the object, the less the BRDF depends on the incident angle and the output angle but is a substantially fixed value. The higher the luster of an object, the larger the value of the minor surface reflection component. In other words, there is a great difference in image brightness between a region of high luster and a region of low luster in an image of the object.
Each of the devices and media dealing with images has a brightness range that the device or the medium can reproduce the image. Thus, when an image including subjects differing in luster is output from a device to a medium of a small brightness reproduction range such as a sheet of paper having a matte paper finish, the difference in brightness between the high luster region and the lower luster region cannot be reproduced to a sufficient degree, with the result that the luster texture is impaired.